This invention relates generally to digital imaging systems. More specifically, the present invention relates to a method and apparatus for increasing automation and document classifying ability of such systems.
In the typical digital imaging system a specimen (or document) is illuminated and then scanned at every pixel to obtain analog reflectivity values. The analog reflectivity values are converted to a multi-digital number by an analog-to-digital converter, where the multi-digital number ranges from a minimum value representing the darkest state possible for the pixel, decimal number 0 for example, to a maximum value representing the lightest state possible for the pixel, decimal number 63 for example.
The multi-digit number representing the reflectivity of the pixel is compared to a threshold value (sometimes dynamic), so that the final digitized picture is represented by a single binary digit for each pixel. Stated differently, each pixel in the final digitized picture is stored or displayed in either an "ON" state or an "OFF" state. In comparing the multi-digit number to the threshold value the resulting pixel value is obtained as follows: if the multi-digit value exceeds the threshold value the pixel is determined to be in the "ON" state; if the multi-digit value equals or is less that the threshold value the pixel is determined to be in the "OFF" state.